Plastic containers are easy to form, can be inexpensively produced and have, therefore, been widely used in a variety of applications. Specifically, an olefin resin container of the shape of a bottle of which the inner wall surface is formed by using an olefin resin such as low-density polyethylene and which is formed by direct blow-forming, has been desirably used as a container for containing viscous slurry-like or paste-like fluid contents such as ketchup and the like from such a standpoint that the content can be easily squeezed out.
Further, the bottles containing highly viscous fluid contents are, in many cases, preserved in an inverted state to quickly discharge the contents or to use the contents to the last drop without leaving them in the bottle. It is, therefore, desired that when the bottle is inverted, the viscous content quickly falls down without adhering or staying on the inner wall surface of the bottle.
To satisfy such requirements, for example, a patent document 1 proposes a bottle of a multilayer structure of which the innermost layer is formed from an olefin resin having an MFR (melt flow rate) of not less than 10 g/10 min.
The innermost layer of this multilayer structure bottle has excellent wettability for the oily content. Therefore, if the bottle is inverted or is tilted, then the oily content such as mayonnaise or the like falls down spreading along the surface of the innermost layer and can be completely discharged without adhering or remaining on the inner wall surface of the bottle (on the surface of the innermost layer).
As for the bottles for containing viscous non-oily contents in which plant fibers are dispersed in water like ketchup, a patent document 2 and a patent document 3 are disclosing polyolefin resin bottles having an innermost layer which is blended with a saturated or unsaturated aliphatic amide as a lubricating agent.
The above patent documents 1 to 3 are all trying to improve slipping property of the plastic containers for the contents based on the chemical compositions of the thermoplastic resin compositions forming the inner surfaces of the containers, and are achieving improvements in the slipping property to some extent. However, limitation is imposed on improving the slipping property due to limitation on the kinds of the thermoplastic resins that are used and on the additives, and striking improvement has not been achieved yet.
On the other hand, a patent document 4 is proposing a packing material of a composition comprising 100 parts by weight of a polyolefin resin blended with an additive having an HLB of not more than 5.0 in an amount in a range of 0.3 to 3 parts by weight.
The packing material of the patent document 4 exhibits excellent parting property relative to emulsified contents such as chocolate creams and custard creams. Namely, the packing material permits emulsified contents to adhere little and alleviates such an inconvenience that the content adheres in large amounts to the inner surface of, for example, a lid member.
According to the study by the present inventors, however, it was found that the container formed from such a composition is not still capable of exhibiting slipping property to the fluid contents such as sauce and the like.
Further, the present inventors have previously proposed a packing container filled with a content, wherein at least part of the surface that comes in contact with the content is a liquid-permeable surface which holds a liquid different from the content (Japanese Patent Application No. 2012-157744).
This container exhibits very improved slipping property to the fluid contents such as ketchup, sauce, mayonnaise and the like accompanied, however, by a problem in that after the container is formed, the liquid must be applied to the portion that comes in contact with the content. Therefore, a further improvement is necessary.